The present invention relates, in general, to enhancing recovery from a hydrocarbon formation and, in particular, to a self-regulatory lift fluid injection tool for controlling the flow rate of a lift fluid injected into the production tubing to enhance the recovery of formation fluids from a hydrocarbon producing well.
Efficiently producing hydrocarbon fluids from downhole formations is a challenging process involving a multitude of different types of equipment and techniques for recovering the fluids from the selected formation. Normally, when production from a hydrocarbon reservoir is commenced, the fluid pressure present in the formation is sufficient to force the liquids to the surface for recovery. After a period of time, however, the natural formation pressure may decline to a point where the pressure is not sufficient to lift the formation fluids to the surface at the desired rate of recovery. In these instances, alternative methods of enhancing the extraction of hydrocarbon fluids from the formation may be employed to augment recovery of formation fluids.
One method of enhancing the recovery of hydrocarbons from a formation is to decrease the hydrostatic head of the column of fluid in the wellbore. Decreasing the hydrostatic head enhances recovery by reducing the amount of pressure required to lift the fluids to the surface. Decreasing the density of the column of fluid extending from the formation to the surface is a technique utilized to reduce the hydrostatic head of the fluid column. For example, mixing a lower density fluid with formation fluids reduces the overall density of the fluid column and consequently decreases the hydrostatic head.
One way to achieve this is by forcing a lift fluid, typically a gas or hydraulic fluid having low density, down the annulus between the production tubing and the casing of the well. The low density fluid is then injected into the production tubing at one or more predetermined locations where it mixes with formation fluids, lowering the density of the fluid column above the formation. The injection of the low density fluid into the production tubing, however, must be carefully controlled to avoid equipment damage while simultaneously providing for optimal recovery. For example, excessive injection rates can result in pressure surges in the tubing and related equipment. Such pressure surges may produce large and destructive forces within the production equipment.
Control of the injection rate is typically accomplished using a metering means such as an orifice, the size of which is typically determined using a trial and error procedure. Thus, the operator attempts to achieve optimum performance of the well by regulating the rate of injection of the lift fluids with various size orifice valves. In practice, the well operator will typically try several orifice settings, allowing the well to stabilize after each adjustment. Due to the distances, location of the valves and the fluid volumes involved, the operator may spend a significant amount of time in making the adjustments, stabilizing production after each adjustment and collecting comparative data from the different settings to establish performance trends.
Therefore, a need has arisen for a lift fluid injection tool that controls the flow of a lift fluid into the production tubing based upon well parameters in an artificial lift well. A need has also arisen for such a tool that does not require the intervention of the well operator to optimize production from the formation. Additionally, a need has arisen for such a tool that periodically monitors and adjusts the injection rate of the lift fluid.
The present invention disclosed herein provides a self-regulating lift fluid injection tool that controls the flow of a lift fluid into the production tubing based upon well parameters in an artificial lift well. The tool of the present invention does not require the intervention of the well operator to optimize production from the formation. The tool of the present invention monitors and adjusts the injection rate of the lift fluid in response to changes in well parameters, prompting by the operator or simply on a periodic basis.
The tool of the present invention is adapted for placement generally concentrically within production tubing disposed within a well casing. The tool includes a control valve that controls the rate of injection of the lift fluid into the formation fluids being produced through the production tubing. A sensor monitors the flow rate of the formation fluids through the production tubing and providing a signal indicative thereof. An electronics package is communicably coupled to the sensor and generates a control signal in response to the signal received from the sensor. An actuator is communicably coupled to the electronics package and adjusts the position of the control valve to regulate the flow rate of the lift fluid therethrough in response to the control signal.
The sensor may include an impeller that rotates in response to the flow of the formation fluids through the production tubing. The impeller may also be used to control the flow rate of the formation fluids.
The tool includes a power source for providing electrical power. The power source may be a battery pack which may be charged using a downhole generator powered by the flow of the lift fluid through the tool or the flow of formation fluids around the tool.
The tool may be linked to a remote location such as a surface facility using a transmitter either alone or in combination with a receiver, each of which are disposed within the tool.
The electronics package of the tool includes a set of preprogrammed instructions for controlling the actuator. For example, the actuator may incrementally adjust the position of the control valve to increase the rate of injection of the lift fluid when the sensor indicates that the rate of recovery of the formation fluids increased in response to a prior incremental adjustment of the position of the control valve to increase the rate of injection of the lift fluid. Alternatively, the actuator may incrementally adjust the position of the control valve to decrease the rate of injection of the lift fluid when the sensor indicates that the rate of recovery of the formation fluids decreased in response to a prior incremental adjustment of the position of the control valve to increase the rate of injection of the lift fluid.
The control valve may include an orifice plate having an orifice and a poppet that is operably connected to the actuator. The poppet may be advanced and retracted relative to the orifice to control the flow of the lift fluid therethrough.
The self-regulating method for controlling the injection of a lift fluid into formation fluids of the present invention involves disposing a lift fluid injection tool having a control valve and a sensor within the production tubing, monitoring the flow rate of the formation fluids through the production tubing with the sensor and adjusting the position of the control valve in response to the flow rate of the formation fluids, thereby controlling the injection of a lift fluid into formation fluids. The step of monitoring the flow rate of the formation fluids through the production tubing may be accomplished by rotating an impeller in response to the flow of the formation fluids. In the method of the present invention, information may be communicated between the tool and a remote location using transmitter and a receiver disposed within the tool.
The step of adjusting the position of the control valve in response to the flow rate of the formation fluids may involve incrementally adjusting the position of the control valve to increase the rate of injection of the lift fluid when the sensor indicates that the rate of recovery of the formation fluids increased in response to a prior incremental adjustment of the position of the control valve to increase the rate of injection of the lift fluid. Alternatively, the step of adjusting the position of the control valve in response to the flow rate of the formation fluids may involve incrementally adjusting the position of the control valve to decrease the rate of injection of the lift fluid when the sensor indicates that the rate of recovery of the formation fluids decreased in response to a prior incremental adjustment of the position of the control valve to increase the rate of injection of the lift fluid.